Automobile module i

AUTOMOBILE ENGINEERING
Anoop P
Asst. Professor
Dept. of Mechanical
Engg:
MITS, Puthencruz
1
DEPARTMENT OF MECHANICAL ENGINEERING - MITS PUTHENCRUZ

OBJECTIVES
 impart the basic concepts of Automobile parts
and its working
 develop the fundamental ideas used in modern
vehicle technologies.
2

AUTOMOBILE
 The term automobile stands for a vehicle which
can move by itself.
 An automobile is made up of a frame, supported
by body on it.
 It has a power producing unit, a power
transmitting unit.
 These units are in turn connected to wheels and
tire's through transmission system. 3

SYLLABUS
 Module 1
Engines- Types of engines in automobiles-classifications-
engine components working of various systems-present and
future vehicles, engine construction- intake and exhaust
systems. Different combustion chambers, carburettors, diesel
fuel pumps, injectors, single point and multi point fuel
injection-MPFI and CRDI systems -lubricating and cooling
systems.
Vehicle performance-resistance to the motion of vehicle-air,
rolling, and radiant resistance-power requirement-
acceleration and gradeability-selection of gear ratios.
4

Module 2
Transmission prime movers- clutch-principle of friction and
cone clutches –centrifugal clutches, diaphragm clutches and
fluid couplings-Gearbox-necessity and principle. Constant
mesh, sliding mesh, synchromesh gear boxes and epicyclic
gearbox –overdrives. Hydraulic torque converters-semi and
automatic transmission systems - constant velocity and
universal joints. Final drive-front wheel, rear wheel and four
wheel drives-transfer case-Hotchkiss and torque tube drives-
differential-nonslip differential-rear axles-types of rear axles.
Module 3
Steering and Suspension Different steering mechanisms-
Ackermann Steering mechanism. Steering gear boxes -power
steering –types. Suspension systems-front axle, rigid axle and
independent suspensions-anti-roll bar-coil spring and leaf
spring - torsion bar -Macpherson strut- sliding pillar- wish
bone- trailing arm suspensions-Shock absorbers -hydraulic
and gas charged shock absorbers-air suspensions Front axle
types-front wheel geometry-castor, camber, king pin inclination,
toe-in toe out, wheel balancing- wheel alignment.
5

Module 4
Chassis, Brakes and Tyres: Types of chassis and body
constructions-crumble zones, air bags and impact beams.
Braking mechanism and convectional brakes- Drum brakes
and Disc brakes. Vacuum booster, hydraulic and power
brakes, components and attachments of mechanical, hydraulic
and pneumatic brakes-Master cylinder-Tandem cylinder-
working. Anti-lock braking systems-Wheels and Tyres-
tubeless tyres-ply ratings- radial tyres. Different tyre wears-
causes
Module 5
Electrical systems - Battery ignition system circuit-
electronic ignition system alternators - voltage regulators
starting system- bendix and follow through drives –
automotive lighting, accessories and dashboard instruments-
head light and horn with relays-circuit diagrams. Automotive
air conditioning Preventive and breakdown
maintenance- engine testing, servicing-engine overhaul-
engine tuning.
6

REFERENCES/TEXT BOOKS
 Automobile Engineering (Vol. 1 & 2) - K.M.Guptha
 Automotive Mechanics- William H. Course
 Advanced Vehicle Technology-Heinz Hesler
 Automobile Engineering (Vol. 1 & 2)- Kirpal Singh
 Automobile Engineering – R.K.Rajput
7

ENGINES
 Engine is the power plant of the vehicle.
 In general, internal combustion engine with petrol or diesel
fuel is used to run a vehicle.
 An engine may be either a two-stroke engine or a four-
stroke engine.
 An engine consists of a cylinder, piston, valves, valve
operating mechanism, carburetor (or MPFI in modern
cars), fan, fuel feed pump and oil pump, etc.
 Besides this, an engine requires ignition system for
burning fuel in the engine cylinder. 8

ENGINE NOMENCLATURE
9
 Cylinder bore
 Top dead centre
 Bottom dead centre
 Stroke
 Swept volume
 Clearance volume
 Compression ratio

ENGINE CLASSIFICATION
Type of fuel used
 Petrol engine
 Diesel engine
 Gas engine
Type of Ignition
 Spark Ignition engine
 Compression Ignition engine
Cycle of Operation
 Otto cycle
 Diesel cycle
No. of strokes/cycle
 2 stroke
 4 stroke 10

Valve location
 Overhead valve engine
 Side valve engine
Basic Design
 Reciprocating
 Rotary
Arrangement of cylinders
 Inline/Straight engine
 V engine
 Opposed Cylinder engine
 Opposed piston engine
 Radial Engine
11

Air intake process
 Naturally aspirated
 Turbocharged
 Crankcase compressed
Type of cooling
 Air cooling
 Water cooling
Application
 Stationary Engine
 Mobile Engines
 Locomotives
 Marine Engines
12

COMPONENTS OF AN IC ENGINE
13

COMPONENTS/PARTS
 Cylinder
 Cylinder head
 Piston
 Inlet and exhaust valves
 Inlet manifold
 Exhaust manifold
 Connecting rod
 Crank
 Flywheel
14

Cylinder:
It is one of the most important parts of the engine, in which
piston moves to and fro.
Engine Cylinder has to withstand a high temperature and
pressure.
Thus the materials for the engine cylinder should be such
that it can retain high pressure and temperature. (usually
alloys of Iron or Aluminium)
The top of the cylinder is covered by cylinder head.
15

16

Engine Block
The engine cylinders are enclosed with in the engine block.
Usually made of cast iron because of its wear resistance
and low cost.
Passages for the cooling water are cast into the block.
17

18

Inlet and Exhaust Valves
Inlet valves admit the entrance of fuel and air and
outlet valves allow the exhaust gases to escape.
19

20

Cam
Is used for opening and closing of Inlet and Exit Valve in
time.
21

22

Piston
Function of Piston is to transmit the force exerted by the
burning of charge to Connecting Rod.
The pistons are usually made of Aluminium Alloy, chrome
nickel alloy, nickel iron alloy, cast steel etc. which are light
in weight.
They have good heat conducting property and also greater
strength at higher temperatures.
23

24

Piston Rings
Circular Rings made of special cast iron housed in the
circumferential grooves provided on the outer surface of the
piston.
Generally there are two sets of rings.
The function of the upper rings is to provide air tight seal
to prevent leakage of the burnt gases into the lower portion
named as compression rings.
The function of lower rings is to provide effective seal to
prevent leakage of oil into the Engine Cylinder and is
termed as oil rings.
25

Connecting Rod
Is a tapered link of ‘I’ section connected between the piston
and crank shaft whose main function is to transmit force
from the piston to the crank shaft.
The upper end, called the small end is fitted to the piston
using a gudgeon pin and lower end called the big end is
connected to the crank using crank pin.
26

Crank
Is a lever connected between the connecting rod and the
crank shaft.
As the piston reciprocates, it rotates about the axis of the
crank shaft.
Crank Shaft
Function of Crank Shaft is to convert the
Reciprocating Motion of Piston into rotary motion with the
help of Connecting Rod.
27

28

Flywheel
Is a big wheel mounted on the crankshaft whose function is
to reduce fluctuation of speed of the engine within a cycle
and there by maintain speed of the engine constant.
29

Crank Case
A cast iron or aluminium case which holds the Crank
Shaft.
crankcase is the housing for the crankshaft. The enclosure
forms the largest cavity in the engine and is located below
the cylinders.
30

4 STROKE PETROL ENGINE(SI ENGINE)
31

32

4 STROKE DIESEL ENGINE(CI ENGINE)
33

34

COMPARISON
35

36
Compression ratio 6 – 10 16 – 20
Weight Less More
Initial cost Less More
Maintenance cost Less More
Control of Power Quantity governing Quality Governing

2 STROKE ENGINE
37

2 STROKE PETROL ENGINE
38

2 STROKE DIESEL ENGINE
39

COMPARISON
40
Aspects Four Stroke Engines Two Stroke Engines
Completion of cycle 4strokes of the piston or in
two revolutions of the
crankshaft.
2 strokes of the piston or in
one revolution of the
crankshaft.
Flywheel Heavier flywheel is needed. Lighter flywheel is needed.
Power produced
Power produced for same
size of engine is small
Power produced for same
size of engine is more
Cooling and lubrication
requirements
Lesser cooling and lubri-
cation requirements.
Lesser rate of wear and
tear.
Greater cooling and lubri-
cation requirement.
Great rate of wear and
tear.

41
Valve and valve
mechanism
Contains valve and
valve mechanism.
No valves but only
ports
Initial cost
Higher is the initial
cost.
Cheaper in initial cost.
Volumetric efficiency
more due to more time
of induction.
less due to lesser time
for induction.
Thermal efficiencies Higher Lower
Applications
Used where efficiency is
important.
Used where (1) low cost,
(2) compactness, and (3)
light weight is
important

PETROL ENGINE – AIR SYSTEM
42
Air filter Carburetor
Engine
Cylinder
Silencer

43

FUEL SYSTEM
44
Fuel
Storage
Tank
Fuel Pump Fuel Filter Carburetor
Engine
Cylinder

INDUCTION OF FUEL IN SI ENGINES
 The fuel Induction systems for SI engine are
classified as:
 Carburetors
 Throttle body Fuel Injection Systems
 Port Fuel Injection System
 Multi Point Fuel Injection Systems. 45

CARBURETOR
46

PORT FUEL INJECTION SYSTEM
47

THROTTLE BODY FUEL INJECTION SYSTEMS
48

MPFI
 D MPFI
 L MPFI
49

D MPFI
 Fuel metering is regulated by engine speed and manifold
vacuum
 Mixing of fuel takes place inside the manifold pipe
 ECU supplies the information for metering and mixing by
means of sensors
 D MPFI (D Jetronic)
 D- Druck(pressure)
50

L MPFI
 L MPFI (L Jetronic)
 L- Luft(Air)
51

MERITS OF FUEL INJECTION IN THE SI ENGINE
 Absence of Venturi – No Restriction in Air Flow/Higher Vol.
Eff./Torque/Power
 Manifold Branch Pipes Not concerned with Mixture
Preparation
 Better Acceleration Response
 Fuel Atomization Generally Improved.
 Use of Greater Valve Overlap
 Use of Sensors to Monitor Operating Parameters/Gives
Accurate Matching of Air/fuel Requirements: Improves Power,
Reduces fuel consumption and Emissions
 Precise in Metering Fuel in Ports
 Precise Fuel Distribution Between Cylinders
52

DIESEL ENGINE - FUEL SYSTEM
53
Fuel
Storage
Tank
Fuel filter
Fuel pump
(Low
Pressure)
Fuel
Injection
Pump
(High
Pressure)
Fuel
injector
Engine
cylinder

DIAPHRAGM PUMP
54
l. Cam
2. Rocker arm
3. Link
4. Diaphragm
5. Diaphragm spring
6. Pump chamber
7. Inlet valve
8. Outlet valve
9. Outlet pipe
10. Spring

FUEL INJECTION PUMP
55

FUEL INJECTOR
56

ELECTRONIC FUEL INJECTION
CRDI (Common Rail Direct Injection)
57

`
58

 Low pressure pump draws fuel from fuel tank to the high
pressure pump through a filter.
 High pressure pump supplies fuel to a common rail
 High pressure diesel oil is then fed to the individual
injectors.
 Injection occurs at equal intervals.
 The control rack controls the timing and quantity of fuel to
the cylinders
59

MERITS
 More power is developed
 Increased fuel efficiency
 More stability
 Pollutants are reduced
 Particulates of exhaust are reduced
 Exhaust gas recirculation is enhanced
 Precise injection timing is obtained
 Pilot and post injection increase the combustion quality
 The powerful microcomputer makes the whole system more
perfect 60

NECESSITY OF COOLING
 Engine valves warp due to over heating
 Lubricating oil decomposes and forms gummy and
carbon particles
 Thermal stresses are set up in the engine parts and
causes distortion
 Reduces the strength of materials used for piston and
piston rings
 Pre- ignition occurs due to over heating of spark plug
 Over heating reduces the efficiency of engine 61

COOLING SYSTEM
62
Air Cooling or Direct Cooling

Advantages
 Engine design is simpler
 Light in weight
 Less space
Disadvantages
 Not effective when compared to water cooling
 Efficiency of engine is less
 Engine parts are not uniformly cooled
 Not suitable for multi cylinder engines
63

WATER COOLING OR INDIRECT COOLING
64

Advantages
 Cooling is more efficient
 Efficiency of engine is more
 Uniform cooling is obtained
Disadvantages
 More weight, since it uses radiator, pump, fan etc.
 Requires more maintenance
 Water circulating pump consumes more power
65

LUBRICATION SYSTEM
Functions
 Lubricant reduces friction between the moving parts
 Reduces wear and tear
 Minimizes power loss due to friction
 Provides cooling effect
 Reduces the noise created by moving parts
 Acts as a sealing between the cylinder and piston 66

Desirable properties
 Should maintain sufficient viscosity under all ranges of
temperature
 Oil must not vaporize
 Should have high specific heat
 Must be free from corrosive acids, moisture etc.
 Good adhesive quality
 Good cohesive quality
67

MIST LUBRICATION SYSTEM
68

WET SUMP LUBRICATION SYSTEM
 Splash system
 Pressure feed system
69

EXHAUST SYSTEM
70

71
PERFORMANCE OF IC ENGINES

NOMENCLATURE
72
 Indicated power(IP) – power produced inside the
cylinder
 Brake power(BP) – Power obtained from the shaft of
the engine
 IP-FP=BP, FP- frictional power

73
 Indicated thermal efficiency ήth = Indicated power
Fuel Power
Fuel Power = mass of fuel used / sec (kg/s) x calorific
value of fuel (J/kg)
Indicated Power = PxLxAxNxK
P – N/m2 Indicated mean effective pressure
A- m2 Area
N – N/2 for 4S, N for 2S where N= rpm of the engine
K- number of cylinders

74
 Brake thermal efficiency ήbth = Brake Power
Fuel Power
Mechanical efficiency ήm = Brake power
Indicated power
Volumetric efficiency ήv = Actual volume of air intake
Stroke/ Swept Volume

75
ABSORPTION DYNAMOMETER
POWER, P= TXW
T = FXR F=M X G
P= 2∏NT/60

COMBUSTION CHAMBERS IN SI ENGINES
 Design of combustion chamber has an important influence
upon the engine performance and its knock properties.
 The design of combustion chamber involves the
 shape of the combustion chamber,
 the location of the sparking plug and
 the positioning of inlet and exhaust valves.
76

The basic requirements of a good combustion
chamber are to provide:
 High power output
 High thermal efficiency and low specific fuel consumption
 Smooth engine operation
 Reduced exhaust pollutants.
77

DIFFERENT TYPES OF COMBUSTION
CHAMBERS
78

T-HEAD COMBUSTION CHAMBER
Introduced by Ford Motor Corporation in 1908.
79

 Both inlet and exhaust valves are located in engine block
on opposite sides
 Requires two cam shafts for actuating the in-let valve and
exhaust valve separately
 High surface- volume ratio, long flame travel
 Very prone to detonation.
80

L HEAD COMBUSTION CHAMBERS
81

 This was first introduced by Ford motor in 1910-30 .
 It is a modification of the T-head type of combustion
chamber.
 Both intake and exhaust valves are kept side by side with
spark plug located above the valves
Advantages
 Valve mechanism is simple and easy to lubricate.
 Detachable head easy to remove for cleaning and
decarburizing without
 Valves of larger sizes can be provided.
Disadvantages
 Poor turbulence
 Extremely prone to detonation due to large flame length and
slow combustion
 More surface-to-volume ratio and therefore more heat loss.
 Extremely sensitive to ignition timing due to slow
combustion process 82

RICARDO’S TURBULENT COMBUSTION
CHAMBER
Ricardo developed this head in 1919. His main objective was
to obtain fast flame speed and reduce knock in L head design.
83

Advantages
 Minimum surface to volume ratio due to hemispherical shape of the
chamber.
 This design ensures a more homogeneous mixture of air and fuel
 Higher engine speed is possible due to increased turbulence
 Ricardo’s design reduced the tendency to knock by shortening
length of effective flame travel.
 This design reduces length of flame travel by placing the spark plug
in the center of effective combustion space.
Disadvantages
 With compression ratio of 6, normal speed of burning increases and
turbulent head tends to become over turbulent and rate of pressure
rise becomes too rapid leads to rough running and high heat losses.
 To overcome the above problem, Ricardo decreased the areas of
passage at the expense of reducing the clearance volume and
restricting the size of valves. This reduced breathing capacity of
engine, therefore these types of chambers are not suitable for
engine with high compression ratio.
84

OVER HEAD VALVE OR I HEAD COMBUSTION
CHAMBER
The disappearance of the side valve or L-head design was
inevitable at high compression ratio of 8 : 1 because of the
lack of space in the combustion chamber to accommodate the
valves.
85

An overhead engine is superior to side valve at high
compression ratios and is due to following reasons:
 Lower pumping losses and higher volumetric efficiency from better
breathing of the engine from larger valves or valve lifts and more
direct passageways.
 Less distance for the flame to travel.
 Less force on the head bolts and therefore less possibility of
leakage (of compression gases or jacket water).
 Removal of the hot exhaust valve from the block to the head, thus
confining heat failures to the head.
 Absence of exhaust valve from block also results in more uniform
cooling of cylinder and piston.
 Lower surface-volume ratio and, therefore, less heat loss and less
air pollution.
 Easier to cast and hence lower casting cost.
86

Two important designs of overhead valve combustion
chambers are used .
Bath Tub Combustion Chamber
87

 This is simple and mechanically convenient form.
 This consists of an oval shaped chamber with both valves
mounted vertically overhead and with the spark plug at the
side.
The main draw back of this design are:
 both valves are placed in a single row along the cylinder
block. This limits the breathing capacity of engine, unless
the overall length is increased.
 However, modern engine manufactures overcome this
problem by using unity ratio for stroke and bore size.
88

Wedge Type Combustion Chamber
89
 In this design slightly inclined valves are
used.
 This design has given very satisfactory
Performance.
 A modern wedge type design can be seen in
for Plymouth V-8 engine.

F- HEAD COMBUSTION CHAMBER
F- head used by Rover Company
90
F – head used in Willeys jeep.
 In such a combustion chamber one
valve is in head and other in the block.
 This design is a compromise between
L-head and I-head combustion
chambers.

Advantages
 High volumetric efficiency
 Maximum compression ratio for fuel of given octane rating
 High thermal efficiency
 It can operate on leaner air-fuel ratios without misfiring.
Disadvantages
 This design is the complex mechanism for operation of
valves and expensive
 special shaped piston. 91

COMBUSTION CHAMBERS IN CI ENGINES
 The most important function of CI engine combustion
chamber is to provide proper mixing of fuel and air in short
time.
 In order to achieve this, an organized air movement called
swirl is provided to produce high relative velocity between
the fuel droplets and the air.
92

C I engine combustion chambers are classified into two
categories:
 OPEN INJECTION (DI) TYPE :
This type of combustion chamber is also called an Open combustion
chamber. In this type the entire volume of combustion chamber is
located in the main cylinder and the fuel is injected into this volume.
 INDIRECT INJECTION (IDI) TYPE:
In this type of combustion chambers, the combustion space is
divided into two parts, one part in the main cylinder and the other
part in the cylinder head. The fuel –injection is effected usually into
the part of chamber located in the cylinder head.
These chambers are classified further into :
 Swirl chamber in which compression swirl is generated
 Pre combustion chamber in which combustion swirl is induced
 Air cell in which both compression and combustion swirl are induced.
93

DIRECT INJECTION CHAMBERS – OPEN
COMBUSTION CHAMBERS
 An open combustion chamber is defined as one in which the
combustion space is essentially a single cavity with little
restriction from one part of the chamber to the other and
hence with no large difference in pressure between parts of
the chamber during the combustion process.
94

95
Advantages
 Minimum heat loss during compression because of lower surface
area to volume ratio and hence, better efficiency.
 No cold starting problems.
 Fine atomization because of multi hole nozzle.
Drawbacks
 High fuel-injection pressure required and hence complex design of
fuel injection pump.
 Necessity of accurate metering of fuel by the injection system,
particularly for small engines.

Shallow Depth Chamber
In shallow depth chamber the depth of the cavity provided in
the piston is quite small.
This chamber is usually adopted for large engines running at
low speeds. Since the cavity diameter is very large, the squish
is negligible.
Hemispherical Chamber:
This chamber also gives small squish. However, the depth to
diameter ratio for a cylindrical chamber can be varied to give
any desired squish to give better performance. 96

Cylindrical Chamber
 This design was attempted in recent diesel engines.
 This is a modification of the cylindrical chamber in the
form of a truncated cone with base angle of 30°. The swirl
was produced by masking the valve for nearly 1800 of
circumference.
 Squish can also be varied by varying the depth.
Toroidal Chamber
 The idea behind this shape is to provide a powerful squish
along with the air movement, similar to that of the
familiar smoke ring, within the toroidal chamber.
 Due to powerful squish the mask needed on inlet valve is
small and there is better utilization of oxygen. The cone
angle of spray for this type of chamber is 150° to160°.
97

IN DIRECT INJECTION CHAMBERS
 A divided combustion chamber is defined as one in which the
combustion space is divided into two or more distinct
compartments connected by restricted passages.
 This creates considerable pressure differences between them
during the combustion process.
98

RICARDO’S SWIRL CHAMBER
99

PRE COMBUSTION CHAMBER
100

101
Advantages
(i) Due to short or practically no delay period for the fuel entering the main
combustion space, tendency to knock is minimum, and as such running is
smooth.
(ii) The combustion in the third stage is rapid.
(iii) The fuel injection system design need not be critical. Because the
mixing of fuel and air takes place in pre-chamber,
Disadvantages
(i) The velocity of burning mixture is too high during the passage from pre-
chambers, so the heat loss is very high. This causes reduction in the
thermal efficiency, which can be offset by increasing the compression ratio.
(ii) Cold starting will be difficult as the air loses heat to chamber walls
during compression.

ENERGY CELL
102

M COMBUSTION CHAMBER
103

Advantages
 Low rates of pressure rise, low peak pressure.
 Low smoke level.
 Ability to operate on a wide range of liquid fuels
Disadvantages
 Since fuel vaporization depends upon the surface
temperature of the combustion chamber, cold starting
requires certain aids.
 Some white smoke, diesel odour, and high hydrocarbon
emission may occur at starting and idling conditions.
 Volumetric efficiency is low. 104

RESISTANCE TO A MOVING VEHICLE
 When a body moves through a fluid, it is encountered by
resistance (drag)
 In order to maintain motion a force needs to be exerted
along the direction of motion of vehicle
 When vehicle moves the propulsion unit has to exert a
tractive effort sufficient enough to balance the resistance
offered
105

Wind or Air Resistance
It depends upon:
 Shape and size of vehicle body
 Air velocity and its direction
 Speed of the vehicle
 Ra = KAV2
106

Rolling Resistance
Caused due to friction between the wheel tyre and road
surface.
It depends upon the following factors:
 Quality of road surface
 Road surface material
 Wheel inflation pressure
 Type of tyre tread
 Load on the road wheels
Rr= KW
W- weight of vehicle in N
K- constant of rolling resistance 107

Gradient Resistance
It refers to the steepness of the road
Depends upon:
 Weight of the vehicle
 Inclination/gradient of the road
Rg=Wsinθ
Total Resistance R = Ra+Rr+Rg
108

109
P = R*V
ήt
P- Power
R- Total Resistance in N
V- Speed in m/s
ήt – transmission efficiency

THANK YOU !!!!!
110

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